Version 2.1.1

This is second release candidate for version 2.1.
Corrected bug with Trace drawing, when the trace had a "punctated" view. The bug was introduced in Ver 2.1.0;
improved editing of IV table; added correct diagnostics of "big endian" HEKA files created on Mac PowerPC. They are still not supported (and probably will be never supported, as it is dying format), but at least they are reported to the user.
Mathematically correct dealing with uncertainty 0/0 in Goldman-Hodgkin-Katz equation when Vm=0 added.